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AMYOTROPHIC LATERAL SCLEROSIS

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Amyotrophic lateral sclerosis (ALS), often referred to as Lou Gehrig’s disease, causes rapidly progressive muscle atrophy and weakness resulting from the degeneration of both upper and lower motor neurons. ALS leads to varying degrees of spasticity, hyperreflexia, and muscle paralysis, eventually resulting in pulmonary complications and the need for mechanical ventilatory support. Because there is no cure, clinicians attempt to slow disease progression and preserve function as much as possible. Medical management focuses on preventing pulmonary infections and forestalling terminal respiratory failure.

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PATHOPHYSIOLOGY

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Since 2009, 13 genes and loci have been identified that are associated with the disease.1 Inclusions in the TAR DNA-binding protein-43 have been found in both ALS and frontotemporal dementia.2 Environmental exposures are suspected to increase the risk of ALS, but no specific ones have been identified to date.3

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Gross CNS pathology includes frontal cortical atrophy, degeneration of both the corticospinal and spinocerebellar tracts, a reduction in large cervical and lumbar motor neurons, and cranial nerve nuclei degeneration. Both motor and sensory peripheral nerves undergo axonal degeneration and segmental demyelination, including motor end plate and axon terminal involvement.

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CLINICAL FEATURES

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Upper motor neuron demyelination and dysfunction cause limb spasticity, hyperreflexia (including Babinski sign and a brisk jaw-jerk reflex), and emotional lability. Limb weakness, a lower motor neuron dysfunction, is the presenting symptom in 65% of patients.4 Other associated lower motor neuron dysfunctions include atrophy, cramps, fasciculations, dysarthria, dysphagia, and difficulty in mastication. At the time of initial presentation, asymmetric extremity cramping, fatigue, weakness, and atrophy can be seen, most prominently in the upper extremities.5 Facial weakness, dysarthria, tongue weakness, and atrophy can be seen with bulbar lower motor neuron dysfunction. Despite these profound motor findings, sensory and cognitive function is usually spared. Significant extremity atrophy occurs, as do fasciculations, hyperreflexia, foot drop, and claw deformity of the hand. Patients also may develop monotonal speech caused by tongue atrophy, despite the relative sparing of facial and eye movements. Parkinsonian dementia may occur in up to 15% of patients. Other cognitive problems, such as apathy, poor attention, decreased motivation, and altered social skills, can be present. Regardless of the initial symptoms, widespread motor and respiratory dysfunction progress within weeks to months.

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DIAGNOSIS

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Patients with ALS typically present to the ED with their diagnosis firmly established. There are multiple diagnostic criteria of ALS, including El Escorial, Airlie House, and the Awaji-Shima criteria, all of which include upper and lower motor neuron dysfunction in the same anatomic distribution. Patients present with rapidly progressing weakness, muscle atrophy, fasciculations, and hyperreflexia but without other CNS dysfunction, such as cerebellar ataxia, autonomic dysfunction, or involuntary movements.6 Given the variation and complexity of symptoms, diagnosis of ALS can be challenging. The median time to diagnosis is 14 months.1 ALS-like symptoms can be seen ...

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